First work toward moving to a Swing UI for the simulator.

src/main/java/com/loomcom/symon/exceptions/CommandFormatException.java

@@ -1,6 +1,6 @@
 package com.loomcom.symon.exceptions;
 
-public class CommandFormatException extends Exception {
+public class CommandFormatException extends SymonException {
   public CommandFormatException(String msg) {
     super(msg);
   }

src/main/java/com/loomcom/symon/exceptions/FifoUnderrunException.java

@@ -1,6 +1,6 @@
 package com.loomcom.symon.exceptions;
 
-public class FifoUnderrunException extends Exception {
+public class FifoUnderrunException extends SymonException {
   public FifoUnderrunException(String msg) {
     super(msg);
   }

src/main/java/com/loomcom/symon/exceptions/MemoryAccessException.java

@@ -4,7 +4,7 @@ package com.loomcom.symon.exceptions;
  * Exception that will be thrown if access to memory or IO cannot be
  * accessed.
  */
-public class MemoryAccessException extends Exception {
+public class MemoryAccessException extends SymonException {
   public MemoryAccessException(String msg) {
     super(msg);
   }

src/main/java/com/loomcom/symon/exceptions/MemoryRangeException.java

@@ -3,7 +3,7 @@ package com.loomcom.symon.exceptions;
 /**
  * Exception that will be thrown if devices conflict in the IO map.
  */
-public class MemoryRangeException extends Exception {
+public class MemoryRangeException extends SymonException {
   public MemoryRangeException(String msg) {
     super(msg);
   }

src/main/java/com/loomcom/symon/exceptions/SymonException.java

@@ -0,0 +1,14 @@
+package com.loomcom.symon.exceptions;
+
+
+/**
+ * Superclass for all symon Exceptions.
+ */
+public class SymonException extends Exception {
+    public SymonException(String msg) {
+        super(msg);
+    }
+    public SymonException() {
+        super();
+    }
+}